1. Field
The present invention relates to a wireless communication apparatus and a method of controlling the same, and more particularly, to a wireless communication apparatus for reducing interference by a neighboring cell, and a method of reducing interference thereof.
2. Discussion of Related Art
As demands for various multimedia services through mobile wireless communication have been recently increased, various research for improving efficiency of use of a frequency of a wireless communication system and a capacity of the system has been conducted. For example, in order to improve the efficiency of the use of the frequency, research on a cognitive radio communication system enabling a second user to use a band which a first user does not use has been actively conducted, and on the other hand, in order to improve a capacity of the system, research on a small cell technology having an advantage of a cost-effective backhaul connectivity in indoor and outdoor environments, simple installation, and low installation cost has been actively conducted.
The small cell technology includes an open access method and a closed access method. The open access method is a method of allowing any user subscribing to a small cell to access the most efficient small cell, and the closed access method is a method of allowing only a permitted user to access a specific small cell. The closed access method may be effective in managing wireless resources and user security, but neighboring small cells use the same frequency, so that there is a disadvantage in that severe interference may be caused between the neighboring small cells.
In order to solve an interference problem by the use of the same frequency between the small cells, various interference reducing methods have been suggested. One of the suggested methods is an interference alignment method of concentrating an interference signal at a transmission terminal to a specific signal region to maximize a degree of freedom of the remaining signal regions. That is, according to the method, interference is concentrated to one signal region among several signal regions, and a signal is substantially transmitted through the remaining signal regions. However, in the interference alignment method, the small cells need to share all of channel information between the small cells, so that the amount of backhaul data is increased, and thus calculation of the system is complicated. Another one of the methods is a Zero Forcing pre-processing method of removing interference of a user subscribing to a neighboring small cell by a small cell. In the ZF pre-processing method, when there is a user influenced by a small cell itself among users subscribing to a neighboring small cell, the small cell removes the interference of the user subscribing to the neighboring small cell by performing the ZF pre-processing. In this case, only channel information about a user, of which interference is to be removed, is required, so that there is an advantage in that the amount of backhaul data is smaller than that of the interference alignment method, but there is a disadvantage in that a degree of freedom is relatively small, so that a capacity of a system is decreased compared to the interference alignment method.
Accordingly, an interference reducing method of reducing interference between neighboring cells, and decreasing calculation complexity of a system and improving a capacity of the system compared to the method in the related art has been demanded.